Acquired, hereditary epignetic codes could evolve faster than genetic mutations

Lamarckism  – after the French biologist Jean-Baptiste Lamarck (1744–1829) – is the idea that an organism can pass on characteristics that it has acquired during its lifetime to its offspring (soft inheritance). Publication of Charles Darwin’s theory of natural selection, and Mendelian genetics led to the general abandonment of the Lamarckian theory of evolution in biology. Despite this abandonment, interest in Lamarckism has recently increased, as several studies in the field of epigenetics have highlighted the possible inheritance of behavioral traits acquired by the previous generation.

Hard inheritance is the passing down of the constant nucleotide sequence of DNA which only changes by rare random mutation. The very slowness of this rate of mutation – and since mutations are usually not beneficial – has been a problem in explaining the variation and diversity observed in particular species. The variations observed in modern humans and which have presumably been generated within just the last 50,000 to 100, 000 years are difficult to explain by natural selection alone especially since there have only been some 5,000 generations available for this diversity to have been established.

A mechanism has long been sought for soft inheritance where environmental influences can be brought into play. Epigenetic mechanisms leave DNA sequence unaltered but can affect DNA by preventing the expression of genes.

A new paper in Science provides some further evidence that the epigenome may well be the hereditary “carrier” of environmental effects but may also cause much more rapid change than genetic mutations.

Science Daily: A “hidden” code linked to the DNA of plants allows them to develop and pass down new biological traits far more rapidly than previously thought, according to the findings of a groundbreaking study by researchers at the Salk Institute for Biological Studies. The study, published September 16 in the journal Science, provides the first evidence that an organism’s “epigenetic” code — an extra layer of biochemical instructions in DNA — can evolve more quickly than the genetic code and can strongly influence biological traits. ……..

…. Now that they have shown the extent to which spontaneous epigenetic mutations occur, the Salk researchers plan to unravel the biochemical mechanisms that allow these changes to arise and get passed from one generation to the next.

They also hope to explore how different environmental conditions, such as differences in temperature, might drive epigenetic change in the plants, or, conversely, whether epigenetic traits provide the plants with more flexibility in coping with environmental change.

“We think these epigenetic events might silence genes when they aren’t needed, then turned them back on when external conditions warrant,” Ecker said. “We won’t know how important these epimutations are until we measure the effect on plant traits, and we’re just now to the point where we can do these experiments. It’s very exciting.”

Read Article

R. J. Schmitz, M. D. Schultz, M. G. Lewsey, R. C. O’Malley, M. A. Urich, O. Libiger, N. J. Schork, J. R. Ecker.Transgenerational Epigenetic Instability Is a Source of Novel Methylation VariantsScience, 2011; DOI:10.1126/science.1212959

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